feat(router): implement otherwise/routeNotFound hook

We need some way to deal with the following cases:

• Route doesn’t match
• CanActivate returns false
• CanDeactivate returns false

This might not all be implemented the same way.

[electricBonfire]

New to the Party, and Angular2, But I am also looking for an implementation as described by @janneromell

If a user types in any URL, and is not authenticated. I interpreted CanActivate as a place to check for if authenticated and if not return false. However, I would also like to redirect the user to a login page when this happens. (Note: not using this for “real” security, more as a view filter. Data is secured by server).

[Krustie101]

I do not think the “is authenticated” check should be done in the CanActivate handler. It is not the concern of the CanActivate handler of a specific component. And you would have to put it on every component that is a routing target. And how would you distinguish between a “no data present” and a “not authenticated” event?

In the ui-router you have a stateChangeStart event. A similar concept seems to be missing in the angular 2 router, maybe for good reasons? After all, it is already possible to listen to “navigation finish” events.

But I would be wary of giving access to the Router service in a handler (CanActivate or startNavigation handler) in order to change the routing, this could get tricky. At first glance, it seems cleaner if such a navigationStart handler should be able to return something that the router resolves to a new (navigation) Instruction that overrides the original one in exceptional case like an authentication check.